Five individuals severely exposed to rabies by wolf bite and treated with a course of phenolized vaccine alone showed no demonstrable antibodies in their sera until the nineteenth day following the start of treatment. Three of these five individuals died of rabies.On the other hand, twelve individuals similarly exposed, who received antirabies serum plus a course of phenolized vaccine, had demonstrable antibodies early in and throughout the period of observation. One individual who received one dose of serum plus a course of vaccine died of rabies.In view of these results, it is apparent that antibody demonstrable early in and throughout the treatment period, and obtained by the combined use of serum and vaccine, is more effective in preventing rabies after severe exposure than is a course of vaccine alone.